1. Field of the Invention
The present invention relates to a driving force transmitting device for driving a driven unit by two driving units and a camera platform device using the driving force transmitting device.
2. Description of the Related Art
A general mechanism for driving a driven unit by a driving force of a motor via a reducer using a gear or a belt has a driving dead band, which is called backlash or lost motion. The dead band causes such a problem that the start of driving of the driven unit is delayed by a dead band amount when the reverse rotating motion of the motor is performed after the driving is completed once.
In order to solve this problem, in Japanese Patent No. 3,820,546, data obtained by measuring dead band amounts at multiple positions of the reducer is stored, and a speed of a driving source is increased for a period of the dead band after the reverse rotating motion started, to thereby reduce the delay of the driving which is caused by the dead band.
There is also a problem in that the driven unit might be moved by the dead band amount by an external force applied to the driven unit after stopped once and thus shifted from an intended rest position.
In order to solve this problem, in Japanese Patent Application Laid-Open No. 2006-211813, multiple driving sources are stopped at different timings based on a maximum dead band amount to vary dead band amounts and their directions with respect to the driving sources and a driven member, to thereby reduce a position deviation caused by the external force.
In Japanese Patent No. 3,820,546, the dead band amounts are measured to reduce the delay of the driving which is caused by the dead band. However, the following problem is not solved: the driven unit might be moved after stopped once by the dead band amount by the external force applied to the driven unit during the driven unit is rest and thus shifted from the intended rest position.
In Japanese Patent Application Laid-Open No. 2006-211813, when the measured maximum dead band amounts is increased by an impact applied to a device or the wearing of a reducing mechanism, there arises a fear in that an effect of preventing the position deviation caused by the external force may be reduced.